National Instruments NI 6602 User Manual

Also see for NI 6601: User manual Manual User manual User manual User manual

National Instruments NI 6602 User Manual Manual pdf 20 page image

Chapter 2 Device Overview© National Instruments Corporation 2-9 NI 660x User ManualNote Transfer rates may vary depending on your computer hardware, operating systemand system activity. This benchmark data was determined on an AMD Athlon XP 1800computer with 128 MB of PC-2100 DDR RAM running Windows XP and LabVIEW usingone counter of the TIO device. For continuous measurements, the transfer rate is themaximum sustained rate for 30 seconds on one counter.High Precision Clock (NI 6608)The accuracy of your time measurement and pulse generation is determinedby the timing accuracy of your counter clock. The NI 6608 device has anoven-controlled crystal oscillator (OCXO) that provides a highly stable10 MHz clock that you can use as a GATE or SOURCE of a counter. Youcan also use the OCXO as the PXI backplane clock. Modules phase lockedto the PXI backplane clock will acquire the same clock stability as theNI 6608. For more information, refer to the KnowledgeBase at ni.com/support and search using keyword phase lock.Using the OCXO as the SOURCE CounterUsing the OCXO as the timebase source of the counter, you can route the10 MHz clock to CtrnSource.Using the OCXO as the 10 MHz PXI Backplane ClockYour PXI chassis has a built-in 10 MHz backplane clock that isindependently routed to each peripheral slot. An independent buffer on thechassis drives the clock signal to each peripheral slot with a skew of lessthan 1 ns between slots. You can use this common reference clock signal tosynchronize multiple modules in a measurement or control system.Use the OCXO 10 MHz clock to drive the PXI backplane clock so themodules in the other slots can take advantage of the stable timebase.Note On NI PXI-660x devices, the maximum timebase is phase locked to the PXIbackplane clock.To use the OCXO 10 MHz clock as the PXI backplane clock, plug theNI PXI-6608 device into Slot 2, or the slot immediately to the right of thecontroller of the PXI chassis.By default, NI-DAQ software drives the 10 MHz clock from the OCXOonto the PXI CLK10 in pin so that the OCXO is used as the PXI backplaneclock. When the PXI chassis senses a clock on the PXI CLK10 in pin in